This invention relates to methods and apparatus for fabricating microlenses.
Individual microlenses fabricated in accordance with the present invention may typically range in size from a diameter of 50 microns to 1 millimeter.
Binary fabrication processes have been used to fabricating microlenses in the prior art.
A series of masks, masking steps, exposure steps and etching steps are used in binary fabrication.
In conventional binary fabrication a photoresist is applied on top of a substrate, and a series of masks are used in sequence to produce the final microlens oonfiguration. The process involves applying a mask, exposing the photoresist through the mask, developing the photoresist, and then etching the exposed substrate. This sequence of operations is repeated for a second mask. It is usually necessary to repeat this masking, exposing, developing, etching sequence three or more times in order to obtain a microlens having the desired optical performance.
Maintaining the required registration of the masks during the successive masking, exposing, developing and etching sequences can be a problem.
Producing complex microlens designs can become difficult using binary fabrication.
Some lens designs cannot be fabricated by binary fabrication techniques.